The present invention relates in general to a solenoid-operated control valve, and more particularly to a multiple-positioned solenoid-operated control valve wherein a valving member such as a valve spool is located at a plurality of operated positions thereof at least on one side of its normal or neutral position.
As solenoid control valves, there have been used directional control valves, flow control or throttling valves or restrictors, shutoff valves, and so on, wherein a valving member as in the form of a spool or piston axially slidably fitted in a valve body having a plurality of ports is normally held in its normal, neutral or original position by a spring, and moved to its operated position or positions against a biasing or resilient force of the spring by means of a solenoid-operated actuator including a movable iron core and a solenoid coil, thereby changing communicating conditions between the ports and associated flow passages, i.e., changing a flow direction of a working fluid, and its flow rate, i.e., cross sectional area of the passage opening at each port. For example, a directional control valve the valve spool of which is selectively located at two or three positions is referred to as a two- or three-position control valve. In the three-position control valve, the valve spool is normally spring-centered at its neutral position and displaced to the right or left of the neutral position, upon energization of one of two solenoids disposed on both sides of the valve spool, to control communicating conditions of the appropriate ports. In the two-position control valve, on the other hand, the valve spool which is biased in one axial direction thereof by a spring and therefore normally held in its normal or original position, is displaced in the other axial direction upon energization of a solenoid to control the communicating conditions of the ports. A flow control or shutoff valve has a valving or orifice control member which is normally held in its normal position by a spring and which is displaced upon actuation of a solenoid for progressively varying or controlling in steps the volume of fluid that passes through a passage or passages or for closing and opening the passage of the fluid.
In the solenoid-operated control valve known in the art, a valving member has on one or each side thereof only one operated position to which it is displaced when the appropriate solenoid is energized. Although there has been known a manually-operated directional control valve which has five positions, i.e, two operated positions on each side of the neutral or center positon of a valve spool, no known solenoid-operated control valves have a valve spool or other valving member which has plural operated positions on one side of its normal position. In this connection, a solenoid-operated proportioning valve is known wherein a valve spool or piston is controlled to be located at a selected position within a predetermined range of its operating stroke. However, this proportioning type of solenoid-operated control valve requires a complicated operation control circuit, which consequently results in pushing up the cost of a hydraulic or pneumatic circuit in which the control valve is incorporated.